django Grabing form input and edit an instance - django

Question

i'm trying to make a simple inventory app but i'm have trouble with restock logic for instance if i have a new stock bought with diffrent price than the first one i want just get the average price on the whole stock in shell works fine but when i go to my form i always get the form input instead of the desired value, after some investigation i found out that i'm grabbing the instance data using request.POST.get and even before the save quantity = item.quantity!! my question now is how can i grab my input and the instance separately
##models
class Supply(models.Model):
name = models.CharField(max_length=100, unique=True)
quantity = models.PositiveIntegerField()
price = models.DecimalField(max_digits=11, decimal_places=2)
created = models.DateField(auto_now_add=True)
last_modefied = models.DateField(auto_now=True)
def __str__(self):
return self.name
##form
class SupplyForm(forms.ModelForm):
class Meta:
model = Supply
fields = ["name", "quantity", "price"]
#view
def add_supply(request):
form = SupplyForm()
if request.POST:
# getting form input data
name = request.POST.get("name")
quantity = request.POST.get("quantity")
price = request.POST.get("price")
# getting Supply instance
item = Supply.objects.get(name=name)
# instantiating the form
form = SupplyForm(request.POST, instance=item)
if form.is_valid:
# Logic
old_supply = item.quantity * item.price
new_supply = int(quantity) * int(price)
new_quantity = item.quantity + int(quantity)
item.price = (old_supply + new_supply) / new_quantity
item.quantity = new_quantity
form.save()
return redirect("project_list")
return render(request, "restock.html", {"form": form})

Answer 1

found this answer to who ever might need it :
1st remove modelform and make a form.Forms with 2 new fields something like that
#forms
class RestockForm(forms.Form):
name = forms.CharField(max_length="30")
quantity = forms.IntegerField(min_value=0)
price = forms.DecimalField(max_digits=11, decimal_places=2)
new_quantity = forms.IntegerField(min_value=0)
new_price = forms.DecimalField(max_digits=11, decimal_places=2)
#views
def add_supply(request, pk):
#getting the object
item = get_object_or_404(Supply, pk=pk)
# instantiating the form on using initial since its not a model form
form = RestockForm(initial={"name": item.name, "quantity": item.quantity, "price": item.price})
if request.POST:
# getting form extra input data
quantity = request.POST.get("new_quantity")
price = request.POST.get("new_price")
form = RestockForm(request.POST,)
if form.is_valid():
old_supply = item.quantity * item.price
new_supply = int(quantity) * int(price)
_quantity = item.quantity + int(quantity)
item.price = (old_supply + new_supply) / _quantity
item.quantity = _quantity
# important need to save the object
item.save()
return redirect("project_list")
return render(request, "restock.html", {"form": form})
#urls
path('restock/<int:pk>', stock_views.add_supply, name="restock"),